• Implemented a feature that fills in a day-to-day itinerary for any of 2,000 cities around the world using Typescript, Node.js, and React which showed 6% greater 8-week user retention and was featured on [CTV](https://danielkoh.dk/ctv/)• Led a team of 3 engineers to optimize our React Native app by patching dependencies to cache frequently called functions, eliminating performance-related Play Store complaints over 3 months and raising the app rating from 4.6 to 4.7 stars• Collaborated with the lead designer to implement a new mobile web landing page in React for post-ad-click users, increasing start trial rates by 10%• Built a service in Node.js to compile trip plan updates and integrate them into an existing notification system, improving re-engagement and boosting 8-week retention by 4%

• Initiated CSS overhaul to make frontend responsive with flexbox and increase lighthouse score by 30 points• Refactored Java Spring Boot backend to cut down build times by 15x, boosting developer productivity and cutting CI/CD costs• Fixed critical bugs in use of Redux store, unblocking development of key features and receiving praise from stakeholders during sprint review

• Built a Python Flask web app to automate participant selection for research study, reducing processing time from 2 days to 5 seconds and demonstrating scalability for high-efficiency workflows